Shire Fish Passage Enhancement Modeling
The Shire project site is located in the Columbia River Gorge in Washington State. The site offers an opportunity to enhance the tidal hydrological connection to a high quality forested wetland complex.
Waterfall Engineering, LLC teamed with cbec to quantify salmonid habitat availability on the project site during two distinct hydrologic regime periods. The first period extends from April through June (the Spring Model), and is typified by increased Columbia River water surface elevations due to snowmelt within the watershed. The second occurs during the late fall, when Columbia River stages are low and variations in river discharge are largely controlled by pulse releases from the Bonneville Dam (the Fall Model). For this analysis, a one-day period from early November, 2016 was examined as being representative of the hydrologic conditions of this latter period.
cbec developed a 2-dimensional hydraulic model to study inundation extents, discharges, and channel velocities on the project site associated with constant spring-fed inflows to the Yeon Creek system and variations in Columbia River stage during the two aforementioned periods. The model consisted of two 2-D flow areas, joined together by a 1-D weir-and-culvert flow connection, as well as three steady tributary inflows and a downstream unsteady stage boundary. A two-foot contour topography layer was provided by Waterfall Engineering, and a roughness map was created in ArcGIS by visual inspection of high-resolution aerial imagery and imported to RAS-Mapper to create spatially heterogenous Manning’s n-values.